1. Field of the Invention
This invention concerns the preparation of secondary amines, and more particularly the preparation of disecondary amines from diolefins, carbon monoxide, hydrogen and primary amines.
2. Description of the Related Art
Diamines are useful intermediate products finding application in the formation of condensation polymers such as polyamides and in the reaction of polyisocyanates to produce polyureas. Various techniques for preparing diamines are known. For example, see U.S. Pat. Nos. 3,882,181; 4,005,143; 4,159,996; 4,197,260; 4,215,073; 4,218,399 and 4,429,157.
It is further known to prepare amines by reacting an olefin with hydrogen, carbon monoxide and a primary or secondary amine. Various techniques embodying this reaction have also been described.
U.S. Pat. No. 2,422,632 suggests that an olefin may be reacted with carbon monoxide and ammonia or an amine having replaceable hydrogen to form an amide or amine.
U.S. Pat. No. 2,497,310 discloses a process for preparing aliphatic amines by reacting carbon monoxide, hydrogen, ammonia or an amine having at least one hydrogen attached to the amino nitrogen, an organic compound containing olefinic unsaturation, and a catalytic quantity of cobalt.
Further work in this field has been focused primarily on the use of different catalyst systems in an effort to obtain better yields and other improvements. U.S. patents disclosing the various catalyst systems are Nos. 3,947,458; 4,096,150; 4,292,242; 4,179,469 and 4,543,411. Also informative as to these and other variations are Iqbal, Helvetica Chemica Acta, Vol. 54, pp. 1440 to 1445 (1971); Laine, et al., J. Org. Chem. 45, 3370 (1980); Jachimowicz, et al., J. Org. Chem. 47, 445 (1982) and U.S. Pat. No. 4,448,996.
U.S. Pat. No. 3,234,283 to Finch, et al. discloses the synthesis of tertiary amines by the reaction of olefins, secondary amines, carbon monoxide and hydrogen in the presence of certain cobalt carbonyl complexes. Finch, et al. teach that the carbonyl complex contains election-donating trivalent phosphorus compounds such as, for example, trialkyl- or triarylphosphines. The mole ratio of the phosphine to the cobalt is instructed to be between 1 and 2.
U.S. Pat. No. 3,513,200 to Biale describes the preparation of tertiary amines by reaction of secondary amines with an ethylenically unsaturated compound, carbon monoxide and hydrogen in the presence of a complex catalyst comprising a Group VIII noble metal hydride in complex with a biphyllic ligand such as an arylphosphine. Biale teaches that the biphyllic ligand may be added directly to the reaction medium, and is preferably used in excess (e.g. 30% to 300%) of that required to form a complex with the Group VIII noble metal, the complex generally comprising 1 to about 5 moles of biphyllic ligand per atom of the metal.
From a study of the art, one learns that to obtain a high yield of product amine from an olefin, carbon monoxide, hydrogen and an amine using prior art catalyst systems, one must prepare a tertiary amine. One may attempt the preparation of a secondary amine by reacting an olefin with hydrogen, carbon monoxide and a primary amine using prior art methods, but the yield is found to be disappointingly low due to the formation of formamide by-product.
Applicants have discovered, however, that it is possible to prepare secondary amines in good yield from olefins, carbon monoxide, hydrogen and primary amines using a two-step process.